Thymidine phosphorylase is a catabolic enzyme whose activity has been studied extensively in human epidermal keratinocytes. Thymidine phosphorylase is identical to the angiogenic agent platelet derived- endothelial cell growth factor. Studies support the notion that 2- deoxyribose and/or the 2-deoxyrihose-1-phosphate are essential to the activity of TPaseIPDECGF in angiogenesis. These studies suggest that TPase/PDECGF may play a role in wound healing by generating 2- deoxyribose. Two specific objectives are proposed that will clarify the role of deoxyribonucleoside catabolism in wound healing. Specific Objective l: Determine the extent to which deoxynucleoside phosphorylases, thymidine phosphorylase and purine nucleoside phosphorylase and /or their products are mitogenic and angiogenic to human endothelial cells. Specific aim 1a. Use an endothelial cell growth assay to measure the mitogenic effect of TPase, PNP and their products. Specific aim 1b. Use a 3D in vitro assay system to measure tube formation by HUVECs as an estimate of angiogenic activity. Specific Objective 2: Determine the metabolic fate of deoxyribose and/or 2-deoxy-D-ribose- l - phosphate in keratinocytes. Specific aim l. Use thymidine, radiolabelled in the deoxyribose moiety, to determine if deoxyribose could serve as a messenger molecule in vivo. The goal of this program is to generate preliminary data to determine the function of deoxynucleoside catabolism in the process of cutaneous wound healing and to exploit this information to develop a new approach to promote wound healing. The experiments proposed in this pilot and feasibility study will be the basis for a more complete understanding of the interaction of keratinocytes and endothelial cells during wound repair.